1. Field of the Invention
The present invention relates generally to a device and method for monitoring a water level, and more particularly, to a device and method for monitoring a water level, which is capable of setting a water area and a shore area (an area excluding the water area) as monitoring areas and monitoring a variation of the monitoring areas through an image analysis.
2. Description of the Related Art
With development of a variety of image equipments, a monitoring system has a wide range of applications to monitoring fields such as monitoring of a particular object by tracking the object through an analysis of an image picked by relevant image equipment or setting a particular basis in the image. Such a monitoring system is becoming increasingly more sophisticated and continues to grow due to a variety of algorithms applied to the image equipments for the image analysis.
An example of fields for which the image equipments are used may include a water level measuring field for measuring or monitoring a water level and informing peoples of a danger based on a result of the measurement or monitoring.
There has been also conventionally used a water level measuring system in which a water level is recognized through detection of an air pressure of a water level sensor if the water level reaches a predetermined value and warning or water level measuring is performed based on the recognition.
However, such a water level measuring system using the water level sensor has a problem of low accuracy due to deviation of the sensor by a flow of water and contamination of the sensor by water.
In addition, there has been also proposed a water level measuring system using an ultrasonic wave or a laser, which has a problem of low accuracy due to increase in a sensor error which may occur when a water surface is irregularly changed or water temperature is varied.
Accordingly, in order to overcome these problems, there has been recently proposed a water level measuring system using image equipments as shown in FIG. 1, which uses a camera 10 to acquire an image for an area occupied by water W in a vertical direction, calculates the number of pixels in a vertical direction X from a boundary B up to the screen lowest point on a still image, and calculates an actual water level based on the calculated number of pixels and preset reference information, thereby overcoming problems due to mechanical malfunction of existing sensors.
However, such a water level measuring system employs an algorithm to calculate the number of pixels in the vertical direction and measure a height based on a preset operation expression, which has a problem in that it is difficult to detect the correct number of pixels as a water surface is irregularly moved due to external environmental factors (wind, movement of particular objects, and so on), and an error of a finally calculated water level increases with increase in an error of the number of pixels.
For example, if a water level instantaneously rises at a particular portion due to an external environmental factor such as wind, measurement including all of corresponding pixel heights is made and thus the water level is measured to be instantaneously higher. Accordingly, a warning system associated with the water level measuring system may make malfunction such as raising an alarm even though the actual water level is not high.
In addition, the calculation of all pixels from the boundary up to the screen lowest point may lead to increase in computation and system complexity, which results in inefficiency of a system for monitoring a water level based on a boundary to a certain water level.
In addition, the above-mentioned water level measuring system has also other problems in that a measurement error occurs due to a change in water surface color by external environmental factors (muddy water, algal bloom and the like), particularly a severe water level measurement error due to difficulty in boundary detection due to the change in water surface color.